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| Test | Information | Notes |
|---|---|---|
| Lab Tests | ||
| Troponin I/T | Myocardial infarction diagnosis | Elevated within hours; peaks at 24–48h; specific for cardiac injury |
| Alkaline Phosphatase (ALP) | Bone and hepatobiliary pathology | ↑ in bone growth, liver obstruction; check GGT for hepatic specificity |
| LDH | Marker of cell turnover or injury | Elevated in hemolysis, MI, cancers, pneumocystis pneumonia |
| INR / PT / PTT | Coagulation pathway evaluation | INR/PT = extrinsic (VII) PTT = intrinsic (VIII, IX, XI, XII) both ↑ in DIC |
| CA-125 | Ovarian cancer marker | Non-specific High in endometriosis, menstruation, peritonitis |
| AFP (Alpha-Fetoprotein) |
Hepatocellular carcinoma, yolk sac tumor, NTDs | ↑ in HCC, ↓ in Down syndrome also elevated in twin pregnancy |
| CEA (Carcinoembryonic Antigen) |
Colon cancer marker | Low specificity used to monitor recurrence not for screening |
| CA 19-9 | Pancreatic adenocarcinoma marker | Elevated in biliary disease too low sensitivity in early disease |
| GGT (Gamma-glutamyl transferase) |
Hepatic enzyme | ↑ in alcohol use and cholestasis distinguishes hepatic ALP from bone |
| Haptoglobin | Marker of intravascular hemolysis | Low in intravascular hemolysis normal in extravascular |
| Reticulocyte Count | Bone marrow response to anemia | ↑ in hemolysis or blood loss ↓ in aplastic anemia or marrow failure |
| Schilling Test | Evaluates B12 absorption | Used to distinguish dietary deficiency vs. pernicious anemia vs. malabsorption |
| Fractional Excretion of Sodium (FENa) | Differentiates AKI causes | <1% suggests prerenal >2% suggests intrinsic renal damage |
| Urine Anion Gap | Assesses cause of non-anion gap acidosis | Positive in renal tubular acidosis negative in GI bicarb loss |
| Urinary Cyanide-Nitroprusside Test | Screens for cystinuria | Turns purple with cystine confirms aminoaciduria |
| Urine osmolality vs. serum osmolality | Evaluates causes of hyponatremia | SIADH = ↑ urine osm DI = ↓ urine osm |
| Urine chloride | Differentiates metabolic alkalosis | Low in vomiting High in Bartter/Gitelman or diuretic use |
| Quantiferon-TB Gold / IGRA | Latent TB screening | More specific than PPD Not affected by BCG vaccine |
| NAAT | STI diagnosis (gonorrhea/chlamydia) |
Gold standard; detecting bacterial DNA/RNA |
| Dark-field microscopy | Treponema pallidum detection | Used for 1° syphilis visualizes spirochetes |
| PAS stain of intestinal biopsy | Diagnoses Whipple disease | Stains Tropheryma whipplei-laden macrophages |
| AFB (Acid-Fast Bacilli) stain | Tuberculosis & Nocardia | Ziehl-Neelsen stain highlights acid-fast organisms |
| CSF 14-3-3 protein | Marker for prion disease | Creutzfeldt-Jakob disease |
| EEG: triphasic waves | Findings in hepatic encephalopathy | Correlateed w/ metabolic encephalopathy |
| CSF albuminocytologic dissociation | Guillain-Barré syndrome | ↑ protein with normal WBC count in CSF |
| Edrophonium (Tensilon) Test | Myasthenia gravis diagnosis (historical) | Transient symptom improvement with AChE inhibitor |
| Plasma Metanephrines | Pheochromocytoma screening | High sensitivity Metanephrines = Catecholamine metabolite |
| Water Deprivation Test | Diabetes insipidus vs. Psychogenic polydipsia | In central DI, desmopressin increases urine osm |
| Physical Exam Tests | ||
| Ortolani / Barlow maneuvers | Congenital hip dysplasia screening | Physical exam clicks/clunks with hip instability |